WIMBLEDON, England — Dominika Cibulkova is supposed to get married on Saturday.

Her suddenly spectacular play on grass may get in the way of those plans, though.

Cibulkova, the No. 19 seed, advanced to the quarterfinals of Wimbledon with a gripping 6-3, 5-7, 9-7 victory over No. 3 Agnieszka Radwanska on Monday.

Cibulkova said her wedding date was set for Saturday, the day of the women’s final, because “I never saw myself as such a great grass-court player.” She had reached the quarterfinals here only once before, in 2011.

But Cibulkova, a 27-year-old Slovak, won the grass-court tournament at Eastbourne before arriving at the All England Club, and now she does not seem in a hurry to get to her wedding to Miso Navara in Bratislava.

Monday’s match with Radwanska took three hours, including an 84-minute third set. It was the fourth match between the two this year, and all four have gone three sets and lasted more than two and a half hours.

Radwanska saved three match points in her second-round victory over Ana Konjuh, which also finished 9-7 in the third. And she fought off defeat again and again Monday.

Cibulkova served for the match at 5-4 in the second set, gaining one match point. But Radwanska broke her in the 12th point of the game, then won the next two games to take the set.

Cibulkova broke Radwanska at love at 3-3 in the third set but could not consolidate in the next game. Cibulkova had five break-point opportunities at 5-5, but Radwanska held in an 18-point game.

“Against Aga today, I felt like I have to put six, seven, eight winners to earn the point,” Cibulkova said.

Radwanska had a match point of her own in the next game with Cibulkova serving at 5-6. Cibulkova saved it with a forehand winner.

The closing games of the match were awash in memorable rallies, with seven lasting 15 shots or more. In the final game alone, Cibulkova won rallies of 25, 21 and 19 shots. The last one gave her a match point, which she put away with another forehand winner.

Cibulkova hit 56 winners over all, with 38 from her forehand side. When the match ended, she fell to the grass and cried.

“I would say it was the toughest match in my career so far, physically and also mentally,” Cibulkova said.

She said she would postpone her wedding if she won her quarterfinal against Elena Vesnina on Tuesday. Vesnina, ranked 50th, is in her first Grand Slam quarterfinal at age 29 after defeating her doubles partner, Ekaterina Makarova, 5-7, 6-1, 9-7.

“If we would really have to postpone it, then it will be like dream come true, you know, because nothing better could happen to me, you know, to me in my tennis career,” Cibulkova said.

She added: “I’m just really happy right now with my tennis and with my private life. You know, you can see it on the court.”

While Radwanska and Cibulkova were dueling on Court 3, the No. 5 seed, Simona Halep, and No. 9 Madison Keys were locked in a battle on Court 1.

Halep served for the first set twice but was broken each time, and Keys prevailed in a tiebreaker. Keys then went up a break early in the second set to take a 2-0 lead.

“Then,” Halep said, “I relaxed myself.”

Halep won the next three games and broke Keys at 4-5 to win the second set, when Keys hit groundstrokes into the net on three successive points.

“The most important thing was that I stayed there, I kept my concentration till the end, and I was fighting,” said Halep, who at 24 is the youngest of the veteran-laden group of women’s quarterfinalists.

By the third set, Keys, the 21-year-old American who entered the top 10 two weeks ago, was visibly bothered by cramping. She got only 35 percent of her first serves in during the third set. She double-faulted on break point at 2-3, and Halep held on to take the match.

“Toward the end of the second, I just felt like I couldn’t really move as well anymore,” Keys said. “I felt like my level really dropped after that.”

She added: “I’m sure in, like, two days I’ll look back and see a lot of positives from it, but right now I’m just really frustrated.”

Halep will next face fourth-seeded Angelique Kerber, the Australian Open champion. Kerber dispatched Misaki Doi, 6-3, 6-1, and has not lost a set in the tournament.

“My tennis is getting better and better every day,” Kerber said. “This is what counts in the second week of a Grand Slam.”

Serena Williams’s tennis also seems to be getting better every day, a bad sign for the rest of the field.

The top-seeded Williams won the last nine games in a 7-5, 6-0 victory over Svetlana Kuznetsova.

Kuznetsova did not win another game after earning a break at 4-4 to serve for the first set. A brief rain shower at 5-5 and the ensuing delay to close the Centre Court roof allowed Williams to regroup after a shaky start.

“I had a little time to think about it and just calm down, really just relax,” said Williams, who finished with 14 aces among her 43 winners.

She credited her coach, Patrick Mouratoglou, for his composure “because I’m really worked up a lot.”

“It helps me realize that when I’m calm, I usually can find answers and I can usually come through in big matches that I want to,” she said.

On Tuesday, Williams will face a former pupil of Mouratoglou’s, 21st-seeded Anastasia Pavlyuchenkova of Russia. She advanced to the Wimbledon quarterfinals for the first time with a 6-3, 6-3 victory over 27th-seeded CoCo Vandeweghe of the United States.

For Pavlyuchenkova, it is a long-awaited breakthrough. She was a three-time Grand Slam junior singles champion. But the day after her 25th birthday, she achieved her best result at a major tournament since the 2011 United States Open.

Like her sister Serena, Venus Williams also came storming back from a slow start, defeating No. 12 Carla Suárez Navarro, 7-6 (3), 6-4. The eighth-seeded Williams, 36, is the oldest woman to reach the quarterfinals at Wimbledon since Martina Navratilova was runner-up at 37 in 1994.

She is in the quarterfinals here for the 12th time, but the first since 2010.

“I’ve been here before,” said Williams, a five-time Wimbledon champion. “I’m not, like, a deer in the headlights. So, of course, I want more.”

Her opponent, 96th-ranked Yaroslava Shvedova of Kazakhstan, will be playing in her first Wimbledon quarterfinal after taking out the No. 28 seed, Lucie Safarova, 6-2, 6-4. Shvedova, 28, came into this tournament having not won a main-draw match on the WTA Tour since early April.

A version of this article appears in print on , on Page B9 of the New York edition with the headline: A Wedding May Wait as a 19th Seed Advances Beyond Her Expectations. Order Reprints | Today’s Paper | Subscribe